One of the two atrio-ventricular valves in the heart is the mitral valve, which is located on the left side of the heart and which forms or defines a valve annulus and valve leaflets. The mitral valve is located between the left atrium and the left ventricle, and serves to direct oxygenated blood from the lungs through the left side of the heart and into the aorta for distribution to the body. As with other valves of the heart, the mitral valve is a passive structure in that it does not itself expend any energy and does not perform any active contractile function.
The mitral valve includes two moveable leaflets that open and close in response to differential pressures on either side of the valve. Ideally, the leaflets move apart from each other when the valve is in an open position, and meet or “coapt” when the valve is in a closed position. However, problems can develop with valves, which can generally be classified as either stenosis, in which a valve does not open properly, or insufficiency (also called regurgitation), in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve. The effects of valvular dysfunction vary, with mitral regurgitation or backflow typically having relatively severe physiological consequences to the patient. Regurgitation, along with other abnormalities of the mitral valve, can increase the workload placed on the heart. The severity of this increased stress on the heart and the patient, and the ability of the heart to adapt to it, determine the treatment options that are available for a particular patient. In some cases, medication can be sufficient to treat the patient, which is the preferred option when it is viable; however, in many cases, defective valves have to be repaired or completely replaced in order for the patient to live a normal life.
One situation where repair of a mitral valve is often viable is when the defects present in the valve are associated with dilation of the valve annulus, which not only prevents competence of the valve but also results in distortion of the normal shape of the valve orifice. Remodeling of the annulus is central to these types of reconstructive procedures on the mitral valve. When a mitral valve is repaired, the result is generally a reduction in the size of the posterior segment of the mitral valve annulus. As a part of the mitral valve repair, the involved segment of the annulus is diminished (i.e., constricted) so that the leaflets may coapt correctly on closing, and/or the annulus is stabilized to prevent post-operative dilatation from occurring. Either result is frequently achieved by the implantation of a prosthetic ring or band in the supra annular position, which can restrict, remodel and/or support the annulus to correct and/or prevent valvular insufficiency.
As an alternative to remodeling of the mitral valve annulus in some cases, the chordae tendinae (referred to herein as “chordae”) that are attached to the leaflets of the mitral valve can be repaired by surgical replacement of the native chordae with artificial chordae in an attempt to restore normal function to the leaflets. With these types of procedures, at least a portion of one or both of the mitral leaflets are secured to one or more structures within the heart using artificial chord members that have a length that allows the leaflets to open and close normally. These procedures can involve the implantation of sutures, which may be made of ePTFE, for example, and which are attached within the heart using relatively labor-intensive and technically challenging procedures. Such procedures are typically performed using invasive, open-heart surgical procedures that require opening of the thoracic cavity to gain access to the heart, then stopping the heart while utilizing heart bypass procedures. However, the use of such bypass techniques can be traumatic and risky for the patient, particularly in cases where the surgical heart repair process takes a long period of time.
To simplify surgical procedures and reduce patient trauma, there has been a recent increased interest in minimally invasive and percutaneous replacement and/or repair of cardiac valves. Replacement or repair of a heart valve in this way typically does not involve actual physical removal of the diseased or injured heart valve. Instead, in one example, a replacement valve can be delivered in a compressed condition to a valve site, such as the pulmonary or aortic valve site, where it is expanded to its operational state. However, percutaneous replacement of a valve and/or minimally invasive valve repair in the area of the mitral valve has its own unique considerations due to the different physical characteristics of the mitral valve as compared to the pulmonary and aortic valves. There is a continued desire to be able to be able to improve mitral valve repair and replacement devices and procedures to accommodate the physical structure of the heart without causing undue stress during surgery, such as providing devices and methods for repairing the mitral valve in a minimally invasive and/or percutaneous manner.